Methylolhydantoins are colorless, odorless, water soluble compounds that are useful as formaldehyde donors in certain preparations that are susceptible to microbial growth. These preparations may include industrial products such as liquid detergents, water-based surfactants, soft soaps, water-based paints, fabric softeners, room deodorizers/air fresheners, polymer emulsions, protective coatings for textiles, architectural coatings, water-based gels, sealants and caulks, latexes for paper coatings, water-based inks, wood preservatives, and the like. They may also include personal care products such as cosmetics, shampoos, creams, lotions, powder products, and the like.
Methylolhydantoins, such as monomethyloldimethylhydantoins (MDMH) or dimethyloldimethylhydantoins (DMDMH) are typically produced as aqueous solutions, usually by methylolating one mole of DMH with one or two moles respectively of formaldehyde. Particularly, Foelsch, in U.S. Pat. No. 3,987,184, discloses a method for the production of aqueous solutions of DMDMH wherein 1.85 to 2.4 moles of formaldehyde (aqueous) per mole of 5,5-dimethylhydantoin (5,5-DMH) are reacted at a pH of from about 7 to about 9, for a period of about 20 minutes, at a temperature of from about 22.degree. C. to 65.degree. C.
Aqueous solutions of MDMH and DMDMH increase the cost of the product due to the expenses of the solvent and of transporting the volume of the aqueous solutions, however. Therefore, a dry product is desirable. The most simple method of producing a dry product is a separation process which separates the methylolhydantoin from the solvent. However, separation processes typically are tedious and time-consuming and involve one or more processing steps.
Farina et al., U.S. Pat. No. 4,908,456, disclose the production of dry, crystallized methylolhydantoins by mixing hydantoin, a formaldehyde source such as para-formaldehyde, and a catalyst, and then reacting the components at elevated temperatures. However, because the reactants are dry blended and are then heated to extreme temperatures, the equipment required is complicated and is not easily accessible.